The present invention relates to industrial trucks and, particularly, to a lift truck mechanism for handling large sheets of glass.
Lift trucks for stacking and loading of large sheets of glass, which may be referred to as glass handling trucks or merely "glass trucks," have been utilized heretofore for transporting large packs of sheets of glass from one place to another, as in glass manufacturing and storage facilities. In such locations, the sheets are stacked and oriented for stacking in an upright condition. When the sheets are to be transferred from one location to another, it has been the practice in using such trucks to maneuver to a pack of sheets, pick up the pack by the sheet edges while maintaining the upright condition of the sheets, and then relocate the pack of sheets to a storage location or place it accurately on a specially designed pallet (on which it is to be stacked against adjacent sheets in face-to-face relationship on edge).
Because of the danger of breakage of large sheets of glass, which typically may have a width of 20 feet and height of 12-13 feet, in the form of packs of sheets of several inches thickness, glass trucks have been heretofore configured to provide an operator station or so-called bridge located atop the truck and above the mast of the lift mechanism. On such a bridge, the operator is provided with controls for full operation of the truck and has good forward visibility. But, more importantly, the operator is in a location of relative safety to prevent injury in the event of breakage of a sheet or sheets of glass.
Great accuracy is required in placing packs of sheets of glass with such a truck, not only to avoid breakage from handling stresses but also to avoid any misalignment providing unstable stacking of the sheets with consequent risk of sheets slipping or falling from the stack. Such could result in an extremely dangerous condition posing serious potential for death or injury. Lateral positioning of the sheets is required to an accuracy of less than an inch and with the vertical alignment or leveling preferably within an accuracy of .+-.0.5.degree..
Because of their large size, glass trucks have required precise, difficult and time-consumming maneuvering, with the driver sometimes being required to jockey the truck or "back and fill," i.e., repetitively to maneuver the truck in and out to orient it for placing or picking up glass sheets accurately.
Accordingly, it is an object of the invention to provide a glass handling lift truck, or so-called glass truck, and lift mechanism for extremely convenient and highly accurate placement and orientation of glass sheets, as in the form of so-called glass packs.
It is a further object of the invention to provide such a glass truck lift mechanism which is not only extensible and retractable (i.e., movable from front to rear) and controllably liftable but which, in accordance with the invention, is controllably laterally shiftable from side to side as well as slewable to provide azimuthal orientation for purposes for picking up or depositing, i.e., placing, sheets of glass.
Another object of the invention is the provision of such a lift truck mechanism which avoids or reduces the need for the operator to maneuver the truck in a difficult, time-consumming manner for lifting up or depositing glass sheets; and which effectively allows the operator to simply bring the truck into proximity to a loading location, brake it to a stop, and thereafter relocate only the lifting mechanism for lifting up or depositing glass packs.
Another object of the invention is the provision of such a glass truck lift mechanism utilizing a simple arrangement of hydraulic cylinders for effecting both shifting and swinging of the lift mast.
A further object of the invention is the provision of such lift mechanism for use on an existing industrial lift truck which is readily mounted on the truck for conversion thereof for glass handling purposes.
Among other objects of the invention are the provision of such a lift truck and lift mechanism which are constructed with a minimum of mechanical components while providing great strength for safe handling of heavy glass loads.
Other objects and features will be in part apparent and in part pointed out hereinbelow.